The idea of life beyond Earth has fascinated humanity for centuries, possibly even before 1609 when Galileo Galilei first observed the Moon through a ‘spyglass’.
More than two centuries after Galileo, the New York Sun published a series of hoax articles about creatures living on the Moon. Into the early 20th century, the astronomer Percival Lowell argued that there were canals on Mars and, therefore, also intelligent life.
Today, we’re still looking for signs of life somewhere up in space, and asking if Saturn’s moons hold the key to finding it.
Saturn and the Titans
The spectacularly-ringed Saturn is the second-largest planet in our solar system, and at last count, it had 146 moons, not including moonlets.
We can probably rule out the possibility of life on Saturn for many reasons. Saturn is a gas giant made of mostly hydrogen and helium, and astronomers think its core is likely to be superheated molten metal and rock.
The gas giant also sits outside what astronomers call the Goldilocks zone — where conditions are just right for liquid water to exist on a planet’s surface. But the hunt for signs of life gets interesting on Saturn’s moons.
Titan: the surprisingly Earthlike moon
Saturn’s largest moon is named Titan for good reason. Titan is the second-largest moon in our solar system, bigger than the planet Mercury and almost as big as Mars.
In some ways, Titan is surprisingly Earthlike. This frozen world has liquid rivers, lakes and seas on its surface (made of methane and ethane, rather than water), clouds and rain, and an ocean of liquid water — although this ocean is many kilometres beneath the moon’s surface.
Titan is unique because it’s the only moon we know of with a liquid on its surface and a thick atmosphere. The atmosphere gets pretty complicated, with nitrogen and methane splitting apart and recombining to form various organic chemicals. Astronomers are curious about what continually replaces the methane in Titan’s atmosphere, and one theory involves volcanoes of ice, gas, and water.
Although scientists have found no evidence of life on Titan, some consider its hydrocarbon lakes and subsurface oceans promising places to look.
Enter Enceladus
Saturn’s seventh moon, Enceladus, is one of the most fascinating places in our solar system.
Enceladus is less than a tenth of Titan’s size, though still bigger than our own Moon, and it was discovered nearly 135 years after Titan. A giant in name only, Enceladus is the brightest of all Saturn’s moons and the most reflective body in our solar system.
The average temperature near the equator on Enceladus is chilly, around -200°C and fresh, clean ice covers the surface. When the Cassini spacecraft flew by the moon in 2005, scientists were surprised by a cloud of water vapour and ice.
Instead of the cloud coming from surface evaporation, as we see with comets, Cassini found continuous plumes of icy water particles and gas erupting from Enceladus at speeds of around 1,300 km/h. Years of analysis have found that a deep ocean beneath the ice feeds Enceladus’s plumes.
Enceladus’s hydrothermal vents make it one of the prime spots for potential life. As we see on Earth, cold water seeps into Enceladus’s crust, which absorbs minerals and is warmed by the moon’s hot core before erupting like a geyser.
Earth’s scientists discovered thriving ecosystems around our deep-sea hydrothermal vents in the 1970s. It’s not unthinkable we might one day find a different kind of life around similar vents on another world, even if it’s not Enceladus.
Enceladus’s hydrothermal vents make it one of the prime spots for potential life. As we see on Earth, cold water seeps into Enceladus’s crust where it absorbs minerals and is warmed by the moon’s hot core, before erupting like a geyser.
Earth’s scientists discovered thriving ecosystems around our deep-sea hydrothermal vents in the 1970s. It’s not unthinkable we might one day find a different kind of life around similar vents on another world, even if it’s not Enceladus.
Jay Chesters
Author
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